Sulfur hexafluoride

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Sulfur hexafluoride
IUPAC name
Sulfur hexafluoride
Systematic IUPAC name
Other names
Sulfur(VI) fluoride
Sulfuric fluoride
Molar mass 146.06 g/mol
Appearance Colorless gas
Odor Odorless
Density 6.17 g/L
Melting point −50.8 °C (−59.4 °F; 222.3 K)
Boiling point −64 °C (−83 °F; 209 K)
0.003% (25 °C)
Solubility Very soluble in aq. alkali, benzene, ethanol, hexane
Vapor pressure 2.9 MPa (at 21.1 °C)
292 J·mol−1·K−1
−1,209 kJ/mol
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sulfur hexafluoride, sometimes shorted to SF6, is an inorganic, colorless, odorless, non-flammable heavy gaseous chemical compound with interesting properties. Its chemical formula is SF6.



Sulfur hexafluoride is almost chemically inert. It will not burn in air, nor will react with other gases. SF6 will not react with molten sodium, but will react with molten lithium metal. When electric current is applied, SF6 will disproportionate to disulfur decafluoride and fluorine gas:

2 SF6 → S2F10 + F2


Sulfur hexafluoride is a colorless, odorless, inert gas. It is a good electric insulator. Its density of 6.12 g/L at standard conditions is nearly 5 times that of air (1.225 g/L).


Sulfur hexafluoride can be purchased from several companies, such as Praxair, Concordeair, Airgas, ElectronicFluorocarbons in compressed gas cylinders. In Russia, it is marketed under the name "Elegas" (Элегаз), from "electric insulation" and "gas".


Sulfur hexafluoride can be prepared by reacting elemental sulfur with fluorine gas, and then scrubbing the resulting gas in an alkali solution to remove sulfur tetrafluoride. However, because this process requires the highly dangerous elemental fluorine, it's safer to just buy the gas from sellers.


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Sulfur hexafluoride, while not a noble gas, has similar properties, such as being non-toxic and inert. However it can displace the oxygen in lungs and carries the risk of asphyxia if too much is inhaled. SF6 will react with molten lithium, but not with other common metals, making it safe to use as an inert gas.


SF6 cylinders should be stored in cold places away from any heat source. It's best to avoid storing it in the basement though, as in case of a leak, it may displace all air from the room, posing slightly greater asphyxiation hazard that CO2, as it cannot be removed with scrubbers.


Sulfur hexafluoride is one of the most potent greenhouse gases, with a global warming potential of 23,900 times that of CO2. However, given the low amounts of SF6 released compared to other greenhouse gases such as carbon dioxide, its overall contribution to global warming is estimated to be less than 0.2%.


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